In the art of clinical analysis, detection of nucleic substances such as DNAs and RNAs is made through hybridization. This method involves bringing a labeled sample into contact with a solid phase on which a DNA or the like of a sequence complementary to the target nucleic substance is fixed, washing away other materials than the target nucleic substance, and measuring the activity of the labeled material bound to the solid phase.
In the field of clinical analysis, by detecting a target nucleic substance through hybridization, the sequence of the nucleic substance is required to be recognized precisely.
In evaluating a sample by hybridization, it is conventionally and widely known to add surface active agents such as sodium dodecyl sulfate (abbreviated as SDS) or N-lauroyl sarcocine (abbreviated as N-LS); or proteins such as bovine serum albumin (abbreviated as BSA) or casein, for inhibiting nonspecific hybridization. However, such surface active agents and proteins have little nonspecific hybridization inhibitory action, so that the sequence of the nucleic substance cannot be recognized precisely.
Patrick et al. (Nature Biotechnology, 17, 365-370 (1999)) propose to inhibit binding of SNPs of a DNA by applying electrical current on the surface of a DNA chip. This method, however, requires dedicated DNA chips, and cannot be applied to every existing DNA chip.
On the other hand, polymers having a phosphorylcholine-like group are under examination for their possible use in the field of clinical analysis. Polymers having a phosphorylcholine-like group are known to have excellent biocompatibilities such as blood compatibility, ability to inactivate complements, and nonadsorbability of biomaterials, as well as excellent antifouling property and moisture holding property, due to their structures similar to phosphlipids originated from biomembrane. Researches and developments in synthesis and use of the polymers have been actively made for developing bio-related materials that make the most of these properties. JP-7-5177-A, JP-7-83923-A, and JP-10-114800-A disclose highly accurate clinical analysis techniques in which polymers having a phosphorylcholine group inhibit adsorption of proteins by a vessel.
However, it is not known that the sequence of a nucleic substance may be recognized precisely, i.e., nonspecific hybridization may be inhibited, by using particular polymers having phosphorylcholine groups.